In an interview to CNN-IBN TV channel, Advani said: "You have a situation in which the prime minister holds office but has no authority, while the person who wields the authority has no accountability", hinting at Congress president Sonia Gandhi.

"This is not a democracy," said Advani, adding that Manmohan Singh had "voluntarily abdicated authority".

He also said Manmohan Singh's weakness as prime minister was "patently" visible and "very clear".

"I have known cases where the prime minister has proposed some course of action but he is not able to implement it unless he gets clearance from the Congress party president," Advani said.

The BJP leader said: "I described him as a weak prime minister in the context of the fact that I have seen prime ministers earlier who had the support of only four MPs in the house and yet they were never at a disadvantage."

"I have seen Chandrashekar, I have seen H.D. Deve Gowda," Advani added.

His comments come a day after Prime Minister Manmohan Singh, during an interaction with women journalists in New Delhi, said he did not wish to have a television debate with Advani as he did not want to accord Advani the privilege of being "an alternative prime minister".